Process control systems for industrial processes, whether distributed control system (DCS) or supervisory control and data acquisition (SCADA) systems, generally include one or more process controllers communicatively coupled to at least one host (e.g., an operator workstation) and to one or more process control devices (e.g., field devices) configured to communicate via analog, digital or combined analog/digital communication signals and/or protocols. Such process control systems are commonly used in oil and gas, chemical, pharmaceutical, pulp and paper manufacturing and petroleum processes. The field devices can comprise device controllers, valves, valve actuators or positioners, switches, transmitters (e.g., temperature, pressure, level, flow rate, or chemical composition sensors), performing functions within the process control system such as actuators opening and/or closing valves and gauges or sensors measuring process parameters. The process controller receives signals indicative of process measurements made by the field devices and/or other information pertaining to the field devices, uses this information to implement a control routine, and generates control signals over buses and/or other communication lines to the field devices such as actuators to control the operation of the processing equipment of the process control system.
In process control systems there are relatively low complexity gauges and meters and relatively high complexity level gauges or ultrasonic flow meters. The low complexity gauges or meters can include temperature sensors (e.g., a thermocouple or a thermistor) and pressure sensors which only provide at most a look-up table or solve a simple equation for providing the transducer function to report a temperature value or pressure value as an electrical signal typically between 4 to 20 mA, and do not provide any data processing. For such low complexity gauges or meters, most of the data processing is generally performed locally in the device with a relatively less complex processor or by a separate processing unit remotely located in the vicinity of the field device, or even by computers within the control room of the plant (operator stations).
The relatively high complexity level gauges or ultrasonic flow meters are much more complex than the low complexity gauges or meters. For example, a relatively high complexity level gauge performs a level calculation at high precision or a relatively high complexity ultrasonic flow meter provides actual gas velocity profiling on flow cross sections. Since the measuring conditions such as turbulences can occur anytime, this makes the flow computation even more complicated, which might necessitate multiple modelling algorithms, and even call for recalibration of the ultrasonic flow meter equipment, which is to be carried out by servicing performed after shutting down.
The relatively high complexity gauges or ultrasonic flow meter equipment is expensive (e.g., about $5 k to $15 k each) and is all inclusive. Such relatively high complexity level gauges and ultrasonic flow meters include an embedded processor, such as a digital signal processor (DSP), Field-Programmable Gate Array (FPGA), microcontroller unit (MCU) or microcomputer that needs to be fairly powerful to perform the needed heavy and complicated mathematical computations. Their onboard memory must also be large enough to handle various data storage and processing, and their physical size is also large. Thus, the power consumption for these relatively high complexity radar level gauges and ultrasonic flow meters is high and a formidable challenge for future firmware changes or upgrading.